STATE HORTICULTURAL SOCIETY. 



145 



Fig. I. PSYLLA PYRI. 



The species of this genus are somewhat numerous, and, as in Aphis, 

 are usually named after the plant upon which they reside — entomologists 

 taking it for granted that, as a rule, a Psylla or an Aphis will be found on 

 but one species of plant. 



5. Psylla pyri. The Jumping Plant-louse of the Pear-tree. 



This species has the head but moder- 

 ately cleft in front, and produces two 

 if not more broods during the summer. ^^ 

 The young are not covered with a cot- 

 tony substance, but are naked. 



The following history of its opera- 

 tions, derived chiefly from Harris, Kol- 

 lar and others, will, with the descrip- 

 tion given below, enable the orchardist 

 to detect it whenever it invades his 

 premises : 



It infests pear trees, to which its operations appear to be almost 

 exclusively confined, and is found on these, in some of its forms, from 



May to October in the northern sec- 

 tions, and from April to November in 

 the southern sections, and is probably 

 two or three-brooded, varying some- 

 what according to latitude. Accord- 

 ing to Kollar, the European Pear-tree 

 Psylla (which is the same as our spe- 

 cies, it being imported) comes forth 

 from its winter retreat, provided with 

 wings, as soon as the buds of the fruit 

 trees begin to expand. After pairing, 

 the female lays her eggs in great numbers, near each other, on the young 

 leaves and blossoms, or on the newly-formed fruit and shoots. 



The eggs are oblong, yellowish, and look somewhat like grains of 

 pollen. The young insects, soon after they are hatched, resemble young 

 wingless plant-lice (true Aphides), and are of a dark yellow color. They 

 change their skins and color repeatedly, and acquire wing-scales or rudi- 

 mentary wings ; then fix themselves to the bark in rows, and remain suck- 

 ing the sap until about to undergo their last change, when they disperse 

 among the leaves, cast off their skins and aj^pear in their winged form. 



While Kollar is doubtless generally correct in reference to the history 

 of this species, his statement in reference to the eggs and the method of 

 hibernating must be received with some caution. T.eon Defour, in his 

 admirable "Researches upon the Anatomy and Physiology of Hemipter- 

 ous Insects," speaking of the Psylla of the fig (^Psylla jicus'), a closely 

 allied species, remarks that he dissected, at the end of October, a female 

 far advanced in gestation, thereby ascertaining the character of the eggs, 

 which are peculiar. That in November he hunted the leaves and sum- 

 mits of the plants on which these insects had been abundant, but failed 

 11 



Fig. 2. Psylla pyri — pupa : — a, the under 

 side ; b, the upper side. 



